Control circuit



April 15, 1952 SEYBQLD 2,593,350

CONTROL CIRCUIT Filed July 24, 194'? I l I Patented Apr. 15, 1952 CONTROL CIRCUIT Arthur M. Seybold, 'West Orange, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application July 24, 1947, Serial No. 763,294

Claims.

1 My invention relates broadly to a simplified gaseous tube circuit which may be used as a con: trol means for controlling an electrical load of any .kind and more specifically to a keying circuit in which an electrically responsive device is used as a load.

In methods heretofore proposed for controlling a load by a gaseous discharge tube, the systems are limited in keying speed by the .frequency of the alternating current supplied to the tubes. .Also, the capacity to ground of systems in the prior art is of such magnitude as to attenuate appreciably any audio or radio frequency signals superimposed upon the supply voltages, such effect limit the use of tone keying. By means of my invention, a discharge tube can be utilized in such a manner that the switching speed is limited only by the ionization and de-ionization time of the tube.

It is accordingly an object of my invention to keep the capacity to ground small enough so that, if desired, audio frequency or radio frequency signals may be superimposed upon the supply voltages without detrimental attenuation.

In a specific embodiment, my invention utilizes a gaseous discharge tube as a means for energizing an electrical load which is connected in series withit. The load is therefore energized only during the ionization periods of the tube, which periods are controlled by use of an auxiliary tube connected in parallel with the gaseous discharge tube and load combination. The voltage drop across the auxiliary tube is below the ionization potential of the gaseous tube only when the auxiliary tube is conducting normally. Consequently, grid bias control of the auxiliary tube by means of a telegraph key or other switching means will give a positive control of ionization moments of the gaseous tube.

As will appear hereinafter, the load used is limited only by the choice of tubes in the circuit and the power supply available, and either an alternating current or direct current power supply may be used.

The features of my invention which I consider novel are set forth with particularity in the appended -claims. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages, will best be understood from the following description of a specific embodiment, when read in connection with the accompanying drawing in which:

Fig. 1 represents schematically a vacuum tube network embodying my invention; and

, invention.

Referring to Fig. 1, it will be noted that the particular electrical load to be controlled which I have selected for the purpose of illustrating my invention is the screen grid voltage of an oscillator tube 4, but it will be understood that any other type of electrical loadmay be controlled, such as a relay, electrical heater, electrical lamp and the like. The oscillator tube 4 is keyed by voltages across a load resistor I connected between its screen grid 2 and cathode 3. This cathode 3., in the embodiment of my invention disclosed herein, is at the voltage reference level. The screen grid and resistor are ordinarily functionally connected together with the cathode 5, of a gaseous discharge tube 6, the anode 'l of which is connected to the positive side of a voltage supply 8, through a potential dropping resistor 9. The voltage supply source 8 has its negative terminal at the voltage reference level.

An auxiliary tube I0 is provided, having an anode H, a cathode l5, and a control electrode It. The said anode is connected to the anode 'l of the gaseous discharge tube and the said cathode is connected to the voltage reference level, while the control electrode and cathode of the auxiliary tube are connected together through a grid leak resistor I2.

A biasing potential I3 is provided for the auxiliary tube, the positive side of which is connected to the voltage reference level and the negative side of which may be intermittently applied to the control electrode of the tube through an interrupter of any type such as a thermostatic switching device or a telegraph key. For purposes of illustration, I have shown such a telegraph key M.

A specific variation of my invention is shown in Fig. 2 which utilizes a relay l! as the electrically responsive load and which has a signal selective means l8 connected between the control electrode [6 and the cathode [5 of the auxiliary tube l0. Any type of signal may be applied at the input terminals l9 to the selective means and the particular signal used will correspond to the selection circuit. The relay which is used as a the effective voltage across the load resistor, the screen grid voltage of the oscillator tube may be controlled. This voltage across the load resistor is in turn controlled by the extinction moments of the gaseous discharge tube 6. Theexplanation of this phenomenon is that when the latter tube is ionized, current Will flow from the supply voltage 8, through the load resistor I, and through the screen-cathode circuit of the tube being controlled, causing an IR (current-resistance) drop which becomes the screen grid voltage of the vacuum tube 4; but when the gaseous discharge tube is de-ionized, the IR drop across thev load resistor is zero, leaving the screen grid of the vacuum tube eifectively at the voltage reference potential.

Control of the ionization moments of the gaseous discharge tube is obtained by use of the auxiliary tube [0. As' hereinbefore indicated, this tube is connected in parallel with the gaseous discharge tube and the load, and/or load resistor, the latter of which are connected in series. The anode voltage of the auxiliary tube may be obtained from the same supply source 8 as the ionization potential of the gaseous discharge tube. A. potential dropping resistor 9 is used in the common anode supply lead from the supply voltage source 8 to the gaseous discharge tube and the auxiliary tube. When conducting, the auxiliary tube has a low internal resistance with respect to the potential dropping resistors. These resistances, being connected in series with the supply-voltage 8, constitutea voltage divider network. By this arrangement, .when the auxiliary tube is, cond cting with a normal value of plate current, its. internal resistance will be small with respect to the potential dropping resistor, and when non-conducting its internal re istance will be large with respect to it. The corresponding voltage drop across the auxiliary tube will be applied to the anode of the ga eous tube.

Conduction of the auxiliary tube is limited by the application of a negative biasing potential l3 at the control electrodeand its internal resistance then becomes large enough so that the supply voltage 8 is applied to the anodes of the tubes ca sing the gaseous discharge tube to ionize; but when the auxiliary tube conducts, theanode potential of the gaseous discharge tube is decreased below its sustaining potential, and the effective Voltageat the anode of the gaseous discharge tu'be'is kept below its ionization potential as long as the auxiliary tube is conducting normally.

In the diagrammed circuit of Fig. 1, the auxiliary tube normally conducts at zero bias, the value of the grid leak resistor I2 being preferably large in order to minimize the current flowing in the keying contacts I l. Maximum value of the resistor is limited by the grid emission characteristicsof the particular tube used in the circuit. The negative potential I3 is of such magnitude as to limit conduction of the auxiliary tube When impressed upon the control electrode,. so that the lR drop across its internal resistance is above the ionization potential of the gaseous discharge tube.

Thus, energization of the load resistor I is accomplished by closing the telegraph key M, and

de-energization is accomplished by opening the I the load resistor [with a key in the low voltage circuit of the negative supply source I3, arcing and unwanted transients are eliminated.

Converse operation of the auxiliary tube may be accomplished by utilizing a tube that is normally cut off near zero bias and by using a positive keying potential l3. In this case the load resistoris, energized when the key is open and is de-energized when the key is closed. The former operation is preferred when a choice may be made because of the lower keying current.

The load obviously may be a relay or any other electrically responsive device adaptable to my in- .vention and hence does not necessarily have to be a load resistor or the screen grid voltage 'of a vacuum tube as is shown in Fig. 2, in which a signal selective means It replaces the telegraph key and the load is a relay l1. When a signal or a pluralityof signals is applied to the input terminals 19 of the selective circuit the signal corre sponding to the particular selective means used may functionally apply a biasing potential to the control electrode l6 of the auxiliary tube. As is hereinbefore explained, this will result in the load, which is in Fig. 2 the relay, becoming energized.

By using a direct current voltage supply source. the keying time is limited only by the ionization and de-ionization times of the gaseous discharge tube. However, an alternating current source of supply voltage may be usedin place of the direct current supply if the keying time is not greater than the supply .voltage frequency. In the latter case, the ionization time ofthe gaseous discharge tube would depend upon the instantaneous am plitude of the voltage source. The system, when used with an alternating current supply, would necessitate a load with either mechanical or electrical inertia if a pulsating characteristic were found objectionable.

Inasmuch as the capacity from the grid of the auxiliary tube to the voltage reference level is small, an audio or radio frequency may be superimposed upon the grid circuit without detrimental attenuation. A corresponding low value of capacity in the plate circuit of the auxiliary tube permits an audio or radio frequency to be superimposed.

It will be understood that my invention is not limited in use to the particular adaptations herein set forth, and that modifications may be made in the system illustrated without departing from the spirit of my invention. Having thus fully described the nature, construction, and operation of my invention, I wish to secure by, Letters Patent, and claim:

1. Apparatus comprising, in combination, an electrical responsive load, a unidirectional gaseous discharge tube having an anode and a cathode, an auxiliary tube having a cathode, a controlelectrode and an anode, a circuit connecting the discharge path of said gaseous tube in series with said electrical responsive load, the cathode of said discharge tube being connected to said load, a biasing potential for said control electrode, a voltage supply source including a potential dropping device connected to the anodes of both of said tubes and said load energizing the same, and an interrupter to intermittently apply said biasing potential to said control electrode.

2. A circuit comprising, in combination, an electrical load comprising the screen grid resistor of an oscillator tube, a unidirectional gaseous discharge tube having an anode and a cathode, an auxiliary tube having an anode, a cathode and a control electrode, a circuit connecting the anodes of said tubes together, the cathode of said discharge tube to one side of said load resistor, and the cathode of said auxiliary tube to the other side of said load resistor, a first voltage supply source including a potential dropping device connected between said anodes and said auxiliary tube cathode, a second potential source biasing said control electrode and an interrupter intermittently applying said biasing potential source to said control electrode.

3. Apparatus comprising, in combination, a unidirectional gaseous discharge tube, an auxiliary tube having a control electrode, an anode and a cathode, a voltage source, an electrically responsive load, a signal potential, a potential dropping device connecting said voltage source to said tubes, connections whereby said load may be applied in series with the unidirectional discharge path of said gaseous tube, a biasing potential on the said control electrode to allow normal conduc ticn ofsaid auxiliary tube, connections between said control electrode and cathode for utilizing said signal potential to limit conduction of said auxiliary tube, and connections between the plate and cathode of said auxiliary tube whereby the gaseous tube is extinguished when said auxiliary tube is conducting and is ionized when said auxiliary tube is limited in conduction.

4. A keying circuit comprising in combination, a unidirectional gaseous discharge tube having a cathode and anode, a load comprising the key ing circuits of an oscillator connected in series combination with said discharge tube, an auxiliary tube having a cathode, an anode and a con trol electrode, said tube being connected in shunt with said, series combination, said anodes of said tubes being connected together, a keying circuit connected to said control electrode, and means 6 for supplying energy to said tubes and said load.

5. A voltage control device comprising in combination an electrical responsive load device; a unidirectional gaseous discharge tube having an anode and a cathode; an auxiliary tube having at least an anode, a cathode, and a control electrode; and first and second sources of low potential direct current, said load device being connected between ground and the cathode of said discharge tube, the anodes of said tubes being electrically connected and also connected to the positive side of said first potential source through a potential dropping resistor, the cathode of said auxiliary tube being grounded, and the control electrode of said auxiliary tube being grounded through a biasing resistor and connected to the negative side of said second potential source through a keying device, and the positive side of said second potential source and the negative side of said first potential source also being grounded.

ARTHUR M. SEYBOLD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,560,431 Schmidt, Jr. Nov, 3, 1925 1,895,774 Smets et a1 Jan. 31, 1933 1,989,510 Fitzgerald Jan. 129, 1935 1,991,027 ODonovan et a1. Feb. 12, 1935 2,045,542 Koch June 23, 1936 2,297,498 Prast Sept. :29, 1942 FOREIGN PATENTS Number Country Date 369,578 Great Britain 1. Mar. 21, 1932 

